1. Field of the Invention
This invention pertains to restraining devices, and more particularly to apparatus for yieldably restraining a first member against motion away from a second member.
2. Description of the Prior Art
Yieldable tie-downs, sometimes referred to as shock cords, are in widespread use. Such devices find numerous applications in the automotive, recreational and marine fields for retaining a first member in a desired location relative to a second member.
Typically, prior elastic tie-downs comprised an elongated flexible element with a hook attached to each end. The flexible element is usually a rubber strap or elasticized cord that is stretchable along its full length. Full length elasticity results in a tie-down having a restraining force that is dependent on the distance between the hooks. That construction poses certain disadvantages. If the tie-down is slightly too long for the application, the tie-down will be too limber. The only way to obtain increased tension or restraining force is by stretching the tie-down to increase the distance between the hooks. However, such stretching is undesirable because then the distance between the hooks increases even more, and the excess length must be taken up. On the other hand, if the tie-down is slightly too short for the application, the tie-down must be excessively stretched, which may produce unwanted force in the restrained members. Further, excessive stretching can result in permanent elongation or deformation. In addition, full length elastic material is undesirably expensive. Even if the tie-down length between the hooks is correct for the application at hand, the tension produced by that length may be improper. In that case, some way must be found to change either the distance between the restrained members or the overall length of the tie-down to obtain the proper tension.
As a result of the length-tension dependency of prior tie-downs, a user must buy several sizes for his various applications. Alternately, he must buy a tie-down that is excessively long for most applications and devise ways of adapting it to applications requiring shorter lengths.
Thus, a need exists for an elastic tie-down that produces a restraining force that is independent of the distance between the end hooks.